研究者詳細 - 仁科　勇太

Polymer-Brush-Decorated Graphene Oxide: Precision Synthesis and Liquid-Crystal Formation 査読

Ohno Kohji, Zhao Chenzhou, Nishina Yuta

LANGMUIR 35 ( 33 ) 10900 - 10909 2019年8月

Influence of pressure of nitrogen gas on structure and thermoelectric properties of acid-treated PEDOT:PSS films 査読

May Thu Zar Myint, Hirotaka Inoue, Susumu Ichimura, Takeshi Nishikawa, Yuta Nishina, Aung Ko Ko Kyaw, Yasuhiko Hayashi

Journal of Materials Science: Materials in Electronics 30 ( 14 ) 13534 - 13542 2019年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

© 2019, Springer Science+Business Media, LLC, part of Springer Nature. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most commonly investigated conductive polymer due to its unique thermoelectric properties. Several post treatments using various acids have been reported to improve the thermoelectric properties of PEDOT:PSS. In most articles, however, only the role of acids on the structure and thermoelectric properties of PEDOT:PSS were reported. In this article, we report the major role of the pressure of nitrogen gas (N2) on the structure and thermoelectric properties of PEDOT:PSS after treatment with various acids at optimized temperatures. After treatment with acids followed by N2 gas-passing, electrical conductivity enhances significantly. Therefore, N2 gas-passing after acid treatments results in higher thermoelectric properties than other traditional acid treatment methods. The enhancement in electrical conductivity is attributed to the removal of insulating PSS and the conformational change of the PEDOT chain. Furthermore, the pressure of N2 is responsible for the additional conformation of PEDOT chain, favoring the linear orientation of the PEDOT structure and resulting in an improvement of the electrical conductivity.

DOI： 10.1007/s10854-019-01721-2

Bipolar anodic electrochemical exfoliation of graphite powders 査読

Hideki Hashimoto, Yusuke Muramatsu, Yuta Nishina, Hidetaka Asoh

Electrochemistry Communications 104 2019年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE INC

© 2019 The Authors The electrochemical exfoliation of graphite has attracted considerable attention as a method for large-scale, rapid production of graphene and graphene oxide (GO). As exfoliation typically requires direct electrical contact, and is limited by the shape and/or size of the starting graphite, treatment of small graphite particles and powders, the typical form available commercially, is extremely difficult. In this study, GO nanosheets were successfully prepared from small graphite particles and powders by a bipolar electrochemical process. Graphite samples were placed between two platinum feeder electrodes, and a constant current was applied between the feeder electrodes using dilute sulfuric acid as the electrolyte. Optical microscopy, atomic force microscopy, X-ray diffractometry, Raman spectroscopy, and X-ray photoelectron spectroscopy were employed to examine the samples obtained after electrolysis. The results obtained from these analyses confirmed that anodic electrochemical exfoliation occurs in the graphite samples, and the exfoliated samples are basically highly crystalline GO nanosheets with a low degree of oxidation (C/O = 3.6–5.3). This simple electrochemical method is extremely useful for preparing large amounts of graphene and GO from small particles of graphite.

DOI： 10.1016/j.elecom.2019.06.001

Force-driven reversible liquid-gas phase transition mediated by elastic nanosponges 査読

Nomura, Keita, Nishihara, Hirotomo, Yamamoto, Masanori, Gabe, Atsushi, Ito, Masashi, Uchimura, Masanobu, Nishina, Yuta, Tanaka, Hideki, Miyahara, Minoru T., Kyotani, Takashi

NATURE COMMUNICATIONS 10 ( 1 ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Nano-confined spaces in nanoporous materials enable anomalous physicochemical phenomena. While most nanoporous materials including metal-organic frameworks are mechanically hard, graphene-based nanoporous materials possess significant elasticity and behave as nanosponges that enable the force-driven liquid-gas phase transition of guest molecules. In this work, we demonstrate force-driven liquid-gas phase transition mediated by nanosponges, which may be suitable in high-efficiency heat management. Compression and free-expansion of the nanosponge afford cooling upon evaporation and heating upon condensation, respectively, which are opposite to the force-driven solid-solid phase transition in shape-memory metals. The present mechanism can be applied to green refrigerants such as H2O and alcohols, and the available latent heat is at least as high as 192 kJ kg(-1). Cooling systems using such nanosponges can potentially achieve high coefficients of performance by decreasing the Young's modulus of the nanosponge.

DOI： 10.1038/s41467-019-10511-7

"Ultramixing": A Simple and Effective Method To Obtain Controlled and Stable Dispersions of Graphene Oxide in Cell Culture Media 査読

Giacomo Reina, Amalia Ruiz, Diane Murera, Yuta Nishina, Alberto Bianco

ACS APPLIED MATERIALS & INTERFACES 11 ( 8 ) 7695 - 7702 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The last decade has seen an increase in the application of graphene oxide (GO) in the biomedical field. GO has been successfully exploited for its ability to deliver many kinds of drugs into target cells. However, GO toxicity assessment is still controversial. Several studies have demonstrated that GO protein coating is crucial to alleviate the material's toxicity. Besides, coronation leads to the formation of big agglomerates, reducing the cellular uptake of the material and thus its therapeutic efficiency. In this work, we propose a simple and efficient method based on rapid (ultra-turrax, UT) mixing to control protein corona formation. Using the UT protocol, we were able to reduce GO agglomeration in the presence of proteins and obtain stable GO dispersions in cell culture media. By labelling GO with luminescent nanoparticles (quantum dots), we studied the GO internalization kinetic and efficiency. Comparing the "classic" and UT protocols, we found that the latter allows faster and more efficient internalization both in macrophages and HeLa cells without affecting cell viability. We believe that the use of UT protocol will be interesting and suitable for the preparation of next-generation GO-based drug-delivery platforms.

DOI： 10.1021/acsami.8b18304

Chemical functionalization of graphitic nanocarbons

Electrical conductivity and optical bandgap of carbonized cellulose nanofiber papers

D. Fukushima, K. Nagashima, T. Takahashi, T. Yanagida, Y. Nishina, K. Uetani, M. Nogi, H. Koga

2019年1月

シングルショット過渡吸収分光における酸化グラフェンの光還元の励起密度依存性

嵐田雄介, 本山竜央, 石原正輝, 佐和孝嘉, 羽田真毅, 仁科勇太, 片山郁文, 武田淳

日本物理学会講演概要集 74.1 1645 - 1645 2019年

Nishina, Y.

Molecular Technology: Materials Innovation 2019年

Tribological properties of oxidized wood-derived nanocarbons with same surface chemical composition as graphene oxide for additives in water-based lubricants 査読

Kinoshita Hiroshi, Suzuki Kyoko, Suzuki Tsutomu, Nishina Yuta

DIAMOND AND RELATED MATERIALS 90 101 - 108 2018年11月

Specific growth inhibitors of Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, X. campestris pv. campestris, and Clavibacter michiganensis subsp. michiganensis 査読

Geofrey Sing'ombe Ombiro, Taku Sawai, Yoshiteru Noutoshi, Yuta Nishina, Hidenori Matsui, Mikihiro Yamamoto, Kazuhiro Toyoda, Yuki Ichinose

Microbiological Research 215 29 - 35 2018年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier GmbH

Plant pathogenic bacteria cause huge yield losses in crops globally. Therefore, finding effective bactericides to these pathogens is an immediate challenge. In this study, we sought compounds that specifically inhibit the growth of Ralstonia solanacearum. As a result, we identified one promising compound, 1-(4-bromophenyl)-6-methoxy-2,3,4,9-tetrahydro-1H-β-carboline, which inhibited the growth of R. solanacearum (Rs1002) from a pilot library of 376 chemicals provided from RIKEN. We further obtained its structural analogues and assessed their ability to inhibit Rs1002 growth. Then we identified five compounds, named ralhibitins A to E, that specifically inhibit growth of Rs1002 at &gt
5 μg/ml final concentration. The most effective compounds, ralhibitins A, C, and E completely inhibited the growth of Rs1002 at 1.25 μg/ml. In addition, ralhibitins A to E inhibited growth of Xanthomonas oryzae pv. oryzae but not the other bacteria tested at a final concentration of 10 μg/ml. Whereas, ralhibitin E, besides inhibiting R. solanacearum and X. oryzae pv. oryzae, completely inhibited the growth of X. campestris pv. campestris and the Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis at 10 μg/ml. Growth inhibition by these compounds was stable at pH 6–9 and after autoclaving. Because Rs1002 grew in the culture medium in which ralhibitins were incubated with the ralhibitin-insensitive bacteria, the unaffected bacteria may be able to inactivate the inhibitory effect of ralhibitins. These results suggest that ralhibitins might be potential lead compounds for the specific control of phytopathogenic bacteria.

DOI： 10.1016/j.micres.2018.06.005

Investigation of active sites for C-H functionalization on carbon-based catalyst: Effect of nitrogen-containing functional groups and radicals 査読

シングルショット過渡吸収分光法による酸化グラフェンの光還元ダイナミクス

嵐田雄介, 石原正輝, 鈴木貴之, 本山竜央, 佐和孝嘉, 溝手翔太, 羽田真毅, 仁科勇太, 片山郁文, 武田淳

応用物理学会学術講演会講演予稿集 2018.2 747 - 747 2018年9月

Ahmad Muhammad Sohail, Suzuki Hideyuki, Wang Chen, Zhao Min, Nishina Yuta

JOURNAL OF CATALYSIS 365 344 - 350 2018年9月

New insertion support device assisted the accurate placement of tunneled cuffed catheter: First experience of 10 cases

Toshiaki Ohara, Kazufumi Sakurama, Satoshi Hiramatsu, Toshimasa Karai, Toshiaki Sato, Yuta Nishina

JOURNAL OF VASCULAR ACCESS 19 ( 5 ) 501 - 505 2018年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SAGE PUBLICATIONS LTD

Introduction: The tunneled cuffed catheter is used in hemodialysis patients for whom an arteriovenous fistula or arteriovenous graft is not suitable or for bridging usage of them. Accurate placement of a tunneled cuffed catheter is necessary for safe hemodialysis, but placement is sometimes difficult because of individual body differences. We developed a new device to support accurate placement of the tunneled cuffed catheter. In this study, we report our first clinical experience of the device.Methods: We made the device by expanded polytetrafluoroethylene with some special processes. The processes enable it to maintain plasticity and temporary shape in the autoclaved condition. The device is laid on the surface of the patient's body to mark the root of the catheter with a felt-tipped marker before catheterization. That enables us to know the accurate catheter root and tunneled cuffed catheter exit site on the body surface. Ten patients underwent tunneled cuffed catheter insertion according to the marking.Case description: The mean age was 71.3 +/- 12.8 years. The tunneled cuffed catheter was safely placed according to the marking in all patients, and all catheter tips were placed in the right atrium. The mean verification tip location difference before and after catheterization was 0.70 +/- 0.48 cm. This result indicated that the device could assist in inserting a catheter accurately within an error of 1.18 cm. The tunneled cuffed catheters were patent in all the cases, without replacement and complications until the end of bridging use or during the observation period.Conclusion: Our newly developed insertion support device enhances safety and prevents catheter waste during replacement.

DOI： 10.1177/1129729818771884

A facile synthesis of a SnO2/Graphene oxide nano-nano composite and its photoreactivity 査読

Tomoyuki Tajima, Haruko Goto, Masayasu Nishi, Takahiro Ohkubo, Yuta Nishina, Hideaki Miyake, Yutaka Takaguchi

Materials Chemistry and Physics 212 149 - 154 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier Ltd

A novel SnO2/graphene oxide (GO) nano-nano composite was prepared by a facile sol–gel process. X-Ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and nitrogen adsorption–desorption isotherms measurements confirmed the formation of a SnO2/GO nano-nano composite. The photoreaction of this SnO2/GO nano-nano composite was studied via the photodegradation of rhodamine B (RhB). Interestingly, the degradation mode of RhB in oxygen-saturated solution is photocatalytic reaction, but the degradation mode in argon-saturated solution is not photocatalytic reaction.

DOI： 10.1016/j.matchemphys.2018.03.046

Graphene oxide size and oxidation degree govern its supramolecular interactions with siRNA 査読

Giacomo Reina, Ngoc Do Quyen Chau, Yuta Nishina, Alberto Bianco

NANOSCALE 10 ( 13 ) 5965 - 5974 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

Several studies have demonstrated the ability of graphene oxide (GO) to efficiently adsorb small-interfering RNA (siRNA) on its surface and to transport it into cells. However, studies on whether and how siRNA interacts with GO are still inconclusive. In this context, understanding the interaction between GO and siRNA is fundamental to design new efficient gene silencing tools. In this work, the interactions between GO and siRNA molecules were systematically investigated. We focused on how the GO size, oxygenated groups present on the surface and chemical functionalization affect the double helix siRNA structure, using gel electrophoresis, UV-Vis spectroscopy, fluorescence resonance energy transfer (FRET) and circular dichroism (CD). We found that the siRNA secondary structure was clearly altered by the interaction with GO flakes. In addition, we were able to correlate the double strand damage with the size and the oxygenated groups present on the GO sheets. Finally, we demonstrated that GO functionalized with low molecular weight polyethyleneimine (PEI, 800 Da) is able to protect siRNA from structural modifications. We believed that this research effort will improve our understanding of the behavior of GO/siRNA complexes, and thus facilitate the design of appropriate bio/nanointerfaces and new efficient gene silencing systems.

DOI： 10.1039/c8nr00333e

Simultaneous improvement in electrical conductivity and Seebeck coefficient of PEDOT:PSS by N-2 pressure-induced nitric acid treatment 査読

May Thu Zar Myint, Masaki Hada, Hirotaka Inoue, Tatsuki Marui, Takeshi Nishikawa, Yuta Nishina, Susumu Ichimura, Masayoshi Umeno, Aung Ko Ko Kyaw, Yasuhiko Hayashi

RSC ADVANCES 8 ( 64 ) 36563 - 36570 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

As a thermoelectric (TE) material suited to applications for recycling waste-heat into electricity through the Seebeck effect, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) is of great interest. Our research demonstrates a comprehensive study of different post-treatment methods with nitric acid (HNO3) to enhance the thermoelectric properties of PEDOT:PSS. The optimum conditions are obtained when PEDOT:PSS is treated with HNO3 for 10 min at room temperature followed by passing nitrogen gas (N-2) with a pressure of 0.2 MPa. Upon this treatment, PEDOT:PSS changes from semiconductor-like behaviour to metal-like behaviour, with a simultaneous enhancement in the electrical conductivity and Seebeck coefficient at elevated temperature, resulting in an increase in the thermoelectric power factor from 0.0818 to 94.3 W m(-1) K-2 at 150 degrees C. The improvement in the TE properties is ascribed to the combined effects of phase segregation and conformational change of the PEDOT due to the weakened coulombic attraction between PEDOT and PSS chains by nitric acid as well as the pressure of the N-2 gas as a mechanical means.

DOI： 10.1039/c8ra06094k